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Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium that’s resistant to the antibiotics that are usually used for first-line treatment. Like more antibiotic-sensitive strains of staphylococci, MRSA generally colonizes the nose and certain areas of skin. Recent data suggest that MRSA can also colonize the throat even if the nose is not colonized. Colonization does not always result in infection, but can cause skin and soft tissue infection, as well as bloodstream infection, pneumonia, bone infection and other serious (and sometimes fatal) infections.
"Staphylococcus aureus has always been one of the most common causes of bacterial infections," says Donald Goldmann, MD, an infectious disease specialist at Children’s Hospital Boston. "But we now have MRSA strains that are resistant to some of the most commonly used antibiotics. MRSA is a major problem in hospitals and in the community."
Staphylococcal infections, including MRSA, are a frequent cause of health care-related infection, and are associated with considerable morbidity, mortality and excess cost. Patients with weakened immune systems may be especially susceptible. The Centers for Disease Control and Prevention (CDC) estimates that there are approximately 94,000 cases of serious MRSA infections and approximately 19,000 deaths per year. Statistics also show that the proportion of staphylococcal infections due to MRSA have risen in U.S. intensive care units, from 2 percent in 1974 to 64 percent in 2004.
In addition, another strain of MRSA has begun to emerge in otherwise healthy people who have not been recently hospitalized or had any medical procedure. These infections are termed community-associated MRSA infections (CA-MRSA) and usually manifest as skin and soft tissue infections. Severe pneumonia, bloodstream infection, bone and joint infection can also occur.
According to the CDC, approximately 2.3 million people in the United States are colonized with MRSA. Most people are unaware they are colonized, so it’s important that preventive measures be taken to minimize its spread, particularly in high-risk areas, such as hospitals. "It’s generally spread by direct contact between individuals or occasionally by objects in the environment," says Dr. Goldmann. "In the community, transmission can occur in athletic facilities or schools due to contaminated equipment. In hospitals, it’s usually spread on the hands of primary health care providers."
MRSA can survive in the environment for a long time–on surfaces and on hands. Thomas Sandora, MD, MPH, medical director of Infection Control at Children’s, advises clinicians to always "wash their hands frequently, and more often if they have an infection or if are in contact with anyone who has an infection. If they have a wound or a skin abscess make sure it’s covered, and if changing a dressing or having contact with a wound, wash hands very carefully afterward."
Dr. Sandora also notes that health care providers must wear gowns and gloves when seeing patients with MRSA, and should clean and disinfect patient-care equipment and surfaces in order to prevent transfer of microorganisms to other patients and environments.
As with any bacteria, MRSA can cause serious infections that need prompt antibiotic treatment. "MRSA is treatable, but there’s a limited selection of antibiotics that will work," says Dr. Goldmann. According to Dr. Sandora, hospital-acquired strains and community-acquired strains also have different susceptibilities. "The strain acquired in hospitals is resistant to more classes of antibiotics, whereas the strain in the community is resistant only to the main class of antibiotics," he says. However, it isn’t uncommon to find hospital strains that have spread to the community and community strains that have been introduced to hospitals. Dr. Sandora advises that wherever possible, it’s best to get a culture if there’s an infection, so the bacteria can be identified.
In general, the most common treatment for MRSA is an antibiotic called Vancomycin, but recent development of new antibiotics has provided other options. Most antibiotics can be safely used in newborns. Dr. Sandora says that patients with MRSA infections should be referred to Children’s Division of Infectious Diseases for evaluation.
Given the potential harm MRSA can cause, some in the medical community have suggested testing every patient for it who gets admitted to the hospital, but Dr. Sandora thinks that might be overkill. "Right now I wouldn’t say it’s cost effective–in terms of controlling the spread of MRSA–to test every patient," he says. "We do test patients who are at high risk for MRSA infection. We screen all patients who are admitted to the intensive care unit because they are more likely to get an infection. But for people who are healthy and who have no symptoms, MRSA isn’t something to worry about."
Consult with the Division of Infectious Diseases: 617-919-2900
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